The thing with the OST was due to legal reasons - they promised an OST with the special edition, so they had to publish... something. Normally they'd offer Gordon a contract for it who would then recompose the (dynamic) in-game music to listenable album tracks. I think they did in the end, but only after announcing it, pressuring him to start working on it before there was a contract because of legal reasons and it would be his name on the chopping board if they failed to deliver, AND having an audio engineer work on it for six months (Gordon had one) independently.
The two year delay is probably lawyer related?
(1) https://www.reddit.com/r/Doom/comments/gdg25y/doom_eternal_o...
(2) https://medium.com/@mickgordon/my-full-statement-regarding-d...
See https://news.ycombinator.com/item?id=33532078 for his his statement and HN discussion.
https://www.shacknews.com/article/133044/mick-gordon-stateme...